Altered Without Drugs: How the Mind Changes Consciousness on Its Own

What Counts as an Altered State?

We tend to speak about consciousness as though there are two settings:

normal

and

altered.

Reality is considerably messier.

Over the course of an ordinary day, consciousness continually changes.

We wake from dreams.

Become absorbed in music.

Lose track of time.

Drift toward sleep.

Become intensely focused.

Daydream.

Meditate.

Experience fear.

Enter flow.

The boundaries of the body, the passage of time, our awareness of the outside world and even our sense of self are more flexible than ordinary waking life makes them appear.

Then there are more dramatic alterations.

People using psychedelics may report geometric imagery, profound changes in time and space, dissolution of the ordinary sense of self, mystical-type experiences or encounters with apparently autonomous beings.

Ketamine can produce detachment from the body and ordinary reality.

But unusual states can also emerge without introducing a psychoactive drug at all.

That raises an interesting question.

If consciousness can be radically altered through breathing, attention, sensory input, suggestion or sleep—

what exactly is being altered?

Consciousness Is Already Changing

There is no single universally accepted scientific definition of an “altered state of consciousness.”

Researchers generally use the term to describe meaningful changes from a person's ordinary waking experience across dimensions such as:

perception,

attention,

self-awareness,

emotion,

time,

body awareness,

thought,

memory,

and sense of reality.

That means an altered state is not necessarily a hallucination.

Nor does “altered” mean pathological.

Dreaming is altered consciousness.

So is general anesthesia.

Deep contemplative states can qualify.

So can delirium.

The phrase therefore describes a broad family of experiences rather than one specific brain state.

This distinction becomes especially important when comparing non-drug altered states with psychedelics.

Two experiences can feel similar in certain ways without being biologically identical.

Breath: Changing the Body to Change the Mind

Perhaps the most striking recent example comes from breathwork.

Certain practices deliberately increase the rate or depth of breathing for sustained periods.

Practitioners sometimes report:

changes in bodily sensation,

emotional release,

visual phenomena,

altered time perception,

feelings of unity,

euphoria,

and mystical-type experiences.

For years, those reports lived largely outside mainstream neuroscience.

That is changing.

A 2025 study examining high-ventilation breathwork accompanied by music found that the intensity of altered-state experiences was associated with physiological activation and changes in cerebral perfusion involving brain regions associated with interoception and emotional memory. (Neuroimaging study)

Then researchers began comparing the experience more directly with other altered states.

How Psychedelic-Like Can Breathing Become?

A 2026 exploratory randomized study compared high-ventilation breathwork with body-scan meditation in 24 healthy, breathwork-experienced adults, with 12 participants in each condition. Allocation was open-label. (Airways to Alteration study)

Breathwork produced stronger reported effects across measures including:

mystical experience,

oneness,

positive mood,

perceptual alteration,

and emotional breakthrough.

One week later, participants in the breathwork condition also reported greater psychological insight and behavioral change.

The study was small and preliminary. Stress, anxiety, depression and well-being improved over time in both groups, without significant between-group differences in those changes. It did not establish breathwork as a treatment or prove that psychedelic-like experiences caused later changes.

But it demonstrated something important:

a non-drug practice involving changes in respiration can accompany surprisingly profound alterations in subjective consciousness.

The comparison did not isolate breathing from music, facilitation, expectations and the wider session context.

A separate 2026 study involving 30 experienced practitioners examined what happened to the brain during high-ventilation breathwork. (Perfusion and network study)

Researchers observed an approximately 45% reduction in global gray-matter cerebral blood flow during the practice.

Yet the magnitude of that reduction did not itself predict the intensity of the altered state.

Changes involving functional connectivity were more complicated and exploratory. Default-mode-network connectivity did not change significantly at the group level. An association between connectivity changes and subjective intensity depended on one analytical approach and was not significant without global signal regression.

So even here, the simple explanation—

less blood flow equals stronger altered state

—doesn't work.

The brain appears to be doing something more complicated.

Breathwork Is Not a Drug-Free Psychedelic

Phenomenological overlap does not mean equivalence.

Psilocybin primarily produces its characteristic effects through serotonergic signaling involving the 5-HT2A receptor.

Ketamine acts through very different pharmacological pathways involving glutamatergic signaling.

High-ventilation breathwork changes respiration, carbon dioxide levels, acid-base balance, autonomic activity, cerebral blood flow and interoceptive signaling.

Different mechanisms.

Some overlapping experiences.

That distinction is central.

Breathwork may eventually provide researchers with a useful non-pharmacological model for studying altered consciousness precisely because it can generate some psychedelic-like phenomena without a psychedelic drug.

A September 2026 exploratory study of 48 mental-health professionals participating in high-ventilation breathwork found experiences reaching intensity ranges comparable to those reported in separate studies using moderate doses of serotonergic psychedelics. This was not a head-to-head drug comparison. The authors also emphasized that therapeutic relevance and risk remain insufficiently characterized and require controlled trials. (Exploratory workshop study)

And “Drug-Free” Does Not Mean Risk-Free

There is a temptation to assume:

natural = safe.

Physiology does not work that way.

High-ventilation breathwork intentionally changes normal respiratory physiology.

Research describes changes involving:

carbon dioxide,

blood pH,

cerebral circulation,

autonomic activation,

and neuronal excitability.

The more intensive forms should therefore not be treated casually as a harmless way to “trip without drugs.”

That is one reason this article is not a breathwork instruction manual.

The interesting question is not how to induce the strongest possible altered state.

It is why altering something as fundamental as breathing can change conscious experience so dramatically.

Meditation: Changing Consciousness Through Attention

Breathing changes physiology.

Meditation approaches consciousness from another direction:

attention.

The word “meditation” encompasses many different practices.

Some emphasize concentration.

Others cultivate open awareness.

Some involve visualization, mantra, compassion, bodily awareness or sustained observation of experience.

Most meditation does not produce anything resembling a psychedelic state.

But intensive contemplative practice can sometimes involve substantial alterations in:

body boundaries,

time perception,

sense of self,

sensory awareness,

emotional experience,

and feelings of unity.

This presents another intriguing possibility.

Perhaps ordinary consciousness requires continuous maintenance.

Attention may be part of that maintenance.

Change how attention is allocated deeply enough, and aspects of the ordinary model of reality may begin to change with it.

You Don't Need to Hallucinate to Alter Consciousness

This is where popular discussions often go wrong.

An altered state does not need:

visions,

entities,

geometric imagery,

or mystical revelation.

Imagine becoming so absorbed in an activity that two hours seem like twenty minutes.

Your external environment has not changed.

But your experience of time has.

Or consider a meditation practice in which the usual boundary between “observer” and “experience” becomes less distinct.

Nothing necessarily appears that isn't there.

Yet the structure of subjective experience has changed.

Altered consciousness can therefore involve changes in how experience is organized, not merely what someone sees.

Hypnosis: When Suggestion Changes Experience

Hypnosis presents an even stranger case.

Under hypnotic suggestion, some people can experience meaningful changes in:

pain,

perception,

attention,

memory,

movement,

and sense of agency.

A 2024 systematic review examining major theories of hypnosis concluded that hypnotic suggestions can produce substantial changes across behavior, perception, cognition and subjective agency.

What remains unresolved is why.

Researchers continue to disagree about whether hypnosis involves a distinctive altered state or whether its effects can be explained through mechanisms such as attention, expectation, suggestion, dissociation and social cognition.

That disagreement creates a fascinating question.

If suggestion can cause someone to genuinely experience a change in perception—

does it matter whether the brain entered a special “state” to produce it?

The experience changed either way.

When the World Stops Providing Enough Information

Ordinary perception feels passive.

Open your eyes.

See the world.

But neuroscience increasingly describes perception as an active process.

The brain receives incomplete sensory information and continuously interprets it.

What happens when the quality of that external information is deliberately reduced?

Researchers have investigated this using the Ganzfeld.

Participants are exposed to a homogeneous, unstructured field of sensory stimulation—often uniform visual input combined with unstructured sound.

With fewer meaningful external features available, people can begin reporting:

imagery,

perceptual distortions,

changes in time,

altered bodily experience,

and pseudo-hallucinatory phenomena.

Ganzfeld experiments have repeatedly demonstrated measurable changes in subjective consciousness.

More recent work continues to show that these environments can induce altered states involving perceptual, bodily, emotional and introspective changes.

Is the Brain Filling in the Gaps?

One interpretation is particularly interesting.

When reliable sensory information becomes weak or ambiguous, internally generated predictions may play a larger role in determining what we perceive.

A neuroimaging study of multimodal Ganzfeld stimulation found progressive changes in communication between the thalamus and cortex alongside changes in default-mode-network organization.

Intriguingly, the pattern differed from changes researchers had observed with psychedelic drugs.

Again:

similar category of experience.

Different apparent biology.

The finding supports a broader idea:

what we experience as reality may depend on an ongoing negotiation between information arriving from the world and predictions generated by the brain.

When the balance changes, experience changes.

When Perception Starts Creating Something That Isn't There

Sensory manipulation can become even more dramatic.

Controlled flickering light viewed through closed eyes can produce vivid geometric forms, colors and visual phenomena despite no corresponding objects being present in the external environment.

Experimental studies have demonstrated that the nature and intensity of these perceptions can vary with flicker frequency.

The light isn't projecting geometric tunnels onto the retina.

The nervous system is generating the percept.

That makes these phenomena useful for consciousness research.

They expose something normally hidden:

seeing is not the same thing as recording.

Hypnagogia: The Border Between Waking and Dreaming

There is an altered state almost everyone encounters.

Most simply forget it.

As waking consciousness gives way to sleep, people can experience hypnagogia.

Images appear spontaneously.

Voices or fragments of language may emerge.

The body may seem to move, expand, fall or float.

Narratives can form without deliberate thought.

A person may remain partly aware that they are lying in bed while simultaneously entering dreamlike experience.

Research comparing hypnagogia, relaxed waking and Ganzfeld states has found measurable differences in both subjective experience and brain electrical activity.

No drug was introduced.

The brain simply changed state.

Yet an internally generated reality began to appear.

Dreams May Be the Most Familiar Altered State of All

Every night, the brain can create:

places that do not exist,

people who are not present,

conversations that never occurred,

bodies that behave impossibly,

and entire worlds accepted—at least temporarily—as real.

We rarely describe dreaming as hallucination because it is so familiar.

But phenomenologically, dreams demonstrate an extraordinary capacity.

The brain can construct an immersive reality with remarkably little external sensory input.

That fact alone should make psychedelic experiences less alien conceptually.

The machinery required to generate radically different realities was already there.

The Body Is Another Route Into Consciousness

Consciousness is not generated by a brain floating independently from the body.

Changes in:

respiration,

heart rate,

autonomic arousal,

hormones,

temperature,

sleep,

fatigue,

pain,

and physical exertion

can all alter subjective experience.

Even something as familiar as sustained exercise can change mood, pain perception, attention and sense of effort.

These changes are generally far less dramatic than psychedelic experiences.

But they reveal a continuum.

There may be no single border where ordinary consciousness suddenly becomes “altered.”

The system is moving all the time.

Are These Really Psychedelic States?

Sometimes.

In limited ways.

That qualification matters.

High-ventilation breathwork can produce experiences scoring highly on measures also used in psychedelic research.

Meditation can involve self-transcendence or changes in self-boundaries.

Hypnagogia can produce vivid imagery.

Ganzfeld conditions can produce pseudo-hallucinatory perception.

Hypnosis can substantially alter subjective reality.

But these experiences are not interchangeable.

A useful way to think about them is through dimensions rather than labels.

Different altered states may contain different combinations of:

altered perception

time distortion

changes in selfhood

emotional intensity

absorption

bodily changes

mystical-type experience

hallucinatory imagery

changes in agency

Two states may overlap strongly on one dimension and barely at all on another.

Different Roads, Overlapping Experiences

Important: These are broad phenomenological comparisons. Experiences vary greatly between individuals and methods. Similar subjective features do not demonstrate identical neurobiological mechanisms.

Why Can the Brain Do This at All?

This may be the larger question.

We normally experience:

a stable body,

a continuous self,

a predictable world,

linear time,

and a clear distinction between imagination and perception.

Because those features feel stable, we assume they are simply properties of reality.

But altered states reveal how much work the nervous system may be doing to maintain them.

The brain continually integrates:

sensory information,

memory,

expectation,

attention,

internal bodily signals,

and prior knowledge

into a coherent model.

Change enough of those inputs or processes and the model can change.

The external world may remain exactly the same.

Yet subjective reality can become radically different.

Does an Altered State Have Therapeutic Value by Itself?

Not necessarily.

This distinction is particularly important as psychedelic-like breathwork and other non-pharmacological approaches attract clinical interest.

An experience can be:

intense,

beautiful,

frightening,

mystical,

emotionally powerful,

or unforgettable

without necessarily producing a durable therapeutic benefit.

The 2026 breathwork studies are intriguing, but they are early. Researchers themselves emphasize the need for controlled clinical trials before therapeutic claims can be established.

The same principle applies more broadly.

Altered consciousness is an experience.

Therapeutic improvement is an outcome.

The relationship between them cannot simply be assumed.

Perhaps the State Is Only Part of the Equation

An altered state also occurs within a context.

A person's:

expectations,

intentions,

environment,

sense of safety,

social support,

and interpretation

may influence what the experience becomes and what meaning is assigned to it afterward.

That connects altered-state research to the broader concept of set and setting.

It also raises a question that appears repeatedly across psychedelic science:

Is therapeutic value produced primarily by the biological intervention?

By the subjective experience?

By what happens around the experience?

Or through an interaction among all three?

The answer may differ depending on the state, intervention and individual.

What We Know

Human consciousness can be altered substantially without psychoactive drugs.

High-ventilation breathwork can produce pronounced subjective changes, including psychedelic-like and mystical-type phenomena, and recent neuroimaging studies demonstrate substantial accompanying physiological and brain changes.

Meditative practices can alter attention, self-experience and perception, although practices and outcomes vary greatly.

Hypnotic suggestion can change perception, cognition, behavior and sense of agency, even though researchers continue to debate the mechanisms responsible.

Ganzfeld and related sensory manipulations can reliably alter perception and subjective consciousness.

Hypnagogia and dreaming demonstrate that vivid internally generated experiences can emerge naturally as the brain moves between states.

And similar subjective phenomena can arise through very different biological routes.

What We Don't Know

We do not have a single agreed scientific definition separating ordinary from altered consciousness.

We do not fully understand why different interventions can produce overlapping subjective phenomena.

We do not know whether similar experiences generated through different mechanisms have similar psychological consequences.

We do not know which features of an altered state—if any—are responsible for therapeutic benefit.

We do not know whether mystical-type or ego-dissolution experiences are necessary for lasting change.

And we still do not understand how the brain constructs the ordinary experience of being a self inside a stable reality well enough to completely explain what happens when that construction changes.

The Question That Remains

Psychedelics are remarkable partly because of how dramatically they can alter human experience.

But perhaps they reveal something even more remarkable.

The capacity for radically different consciousness does not appear to belong exclusively to the drug.

Breathing can change it.

Attention can change it.

Suggestion can change it.

Sensory input can change it.

Sleep can change it.

The brain can generate worlds while dreaming and perceptions without corresponding objects while awake.

Psychedelics may therefore not give the human mind an entirely foreign capacity.

They may reveal just how radically consciousness was capable of changing all along.

And if the mind can transform its experience of reality while the external world remains unchanged—

how much of what we call reality is being constructed from within?

Sources & Further Reading

This article draws on peer-reviewed research concerning high-ventilation breathwork, meditation, hypnosis, Ganzfeld stimulation, visual flicker, hypnagogia and altered states of consciousness.

Breathwork neuroimaging (2025): Neurobiological substrates of altered states of consciousness induced by high ventilation breathwork accompanied by music, PLOS ONE.

The 24-participant comparison (2026): An exploratory study of breathwork-induced altered states of consciousness in experienced practitioners: the airways to alteration (A2A) trial, Frontiers in Psychology. This was an exploratory randomized study with open-label allocation; its small groups, lack of blinding and self-reported outcomes limit interpretation.

The 30-participant imaging study (2026): How high ventilation breathwork alters consciousness: Hypoperfusion, network dynamics, and subjective experience, Progress in Neuro-Psychopharmacology and Biological Psychiatry. The reported 45.5% average blood-flow reduction was not itself associated with subjective altered-state intensity.

Expert workshop (September 2026): High ventilation breathwork as a non-pharmacological model for inducing psychedelic-like states: expert evaluations of therapeutic potential and risk, npj Mental Health Research. Participants' experiences and opinions do not establish clinical efficacy or safety.

Research into non-pharmacological altered states remains developing. Similarities in subjective experience between two states should not be interpreted as evidence that they share the same biological mechanisms or therapeutic effects.

Editorial Note

Terms such as “psychedelic-like,” “mystical” and “altered state” describe reported phenomenological characteristics. They do not imply that non-pharmacological practices are biologically equivalent to psychedelic drugs or validate metaphysical interpretations of subjective experiences.

Safety Note

Some practices capable of producing altered states—including intensive high-ventilation breathwork and flickering-light stimulation—can involve medical or neurological risks and may not be appropriate for everyone. This article describes research rather than providing instructions for inducing altered states.

Medical Disclaimer

This article is provided for informational and educational purposes only and is not medical advice, diagnosis or treatment.